1. Field of the Invention
The present invention is directed towards a more efficient and less expensive process for biological treatment of aqueous waste and raw animal waste.
2. Background Art
A balanced nitrogen cycle is important to our environment. However, many human activities have perturbed the nitrogen cycle and caused nitrogenous pollution and environmental problems. Fertilizer production, farming of leguminous crops, and fossil fuel combustion contribute to an annual anthropogenic nitrogen fixation of 90, 40 and 20 Tg(N)/yr, respectively. Thus, the overall amount of nitrogen fixation contributed by human activity essentially equals the annual total of naturally-occurring nitrogen fixation, i.e., approximately 130 Tg(N)/yr.
Intake of high-nitrate food (e.g., highly fertilized vegetable, livestock fed with high-nitrate forage material or aquacultural production from an aqueous environment of high nitrate concentrations) has been correlated with increased risk to human health. Nitrate poisoning results from the conversion of nitrate to nitrite in the body. Absorption of nitrite into the blood stream produces abnormal hemoglobin (methemoglobin), which is incapable of transporting oxygen. Nitrates in water or meat are especially hazardous to young infants because their relatively high gastric pH facilitates the reduction of nitrate to nitrite by bacteria causing blue baby syndrome. Nitrite can interact with substrates such as amine and amide to produce N-nitroso compounds including nitrosamines, many of which may cause cancer in many animal species.
Ammonia (NH4+) is recognized as a toxic compound by the National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA). A number of ammonium compounds, i.e., ammonium acetate, ammonium chloride, ammonium nitrate, ammonium sulfide, etc., are also toxic to human beings. Ammonium ions in drinking water, where ammonium ions exist in equilibrium with ammonia and hydrogen ions, may not only cause toxicity but also reduce the disinfecting efficiency of chlorine. Adding additional chlorine to compensate for the presence of ammonia will also cause over-disinfection problems such as producing by-products (e.g. trihalomethanes and total organic halogens), tastes and odors, accelerating corrosion, and increasing costs.
The present invention is directed to an efficient and cheap process of removing NH3/NH4+, NO2xe2x88x92, and NO3xe2x88x92 from aqueous waste. The traditional biological treatment process uses oxidation methods to remove ammonium. However, oxidation of ammonium does not truly remove it but transforms it into NO2xe2x88x92, and NO3xe2x88x92, both of which still remain in the system. A biofilter system of the present invention utilizes an Alternating-Aerobic-Anoxic (AAA) process in a single biological fluidized bed reactor to provide efficient and cheap removal of carbonacious materials, nitrogenous materials and/or mixtures thereof from aqueous waste. This system has great economic advantages over other current nitrogen removal technologies and is believed to be the star of tomorrow. The biofilter system of the present invention is particularly suitable for treating aqueous waste resulting from aquaculture, industrial processes and animal husbandry.
The present invention is directed to a biofilter system for removal of carbonaceous matter, nitrogenous matter, and/or mixtures thereof, from an aqueous source. The biofilter system includes a main biofilter chamber containing therein aerobic and anaerobic bacteria without physical separation; an inlet port and an outlet port connected to the main biofilter chamber; and a means for oxygenating the aerobic and anaerobic bacteria in the main biofilter chamber, including means for timing the oxygenation of the aerobic and anaerobic bacteria. The means for oxygenating the bacteria may include a pump, an agitator and/or an air diffuser. The biofilter system may further comprise a disinfection unit, such as, an ozonizer utilizing ultraviolet light. In one embodiment, the biofilter system may further comprise means for measuring the level of any one of oxygen, nitrogen, organic carbon, phosphate and pH.
In the biofilter system of the present invention, the bacteria in the biofilter chamber can be carried by a solid support, such as, for example, a biotower, a rotating biological contactor, rough stones, slats, plastic media, a reticulated foam particle, a microcarrier and/or media particles. In a preferred embodiment, the bacteria are carried by anionic and hydrophilic media particles having a rough surface, such as ceramic spheres, with a diameter less than 1 mm, or more preferably, either less than 0.8 mm or less than 0.6 mm. In the alternative, the bacteria can be present in the biofilter in suspension, free of a solid support. It is contemplated that the bacteria used in the biofilter system of the present invention are capable of growth in aminobenzene, phenol, monoethylamine, diisopropylamine, and/or mixtures thereof.
Another aspect of the invention provides a method for removal of carbonaceous matter, nitrogenous matter, and/or a mixture thereof from an aqueous source, wherein the removal is carried out by flowing the aqueous source through a biofilter system of the present invention. Accordingly, the method of the present invention includes the steps of: contacting in a biofilter chamber an aqueous waste with a mixture of aerobic and anaerobic bacteria; providing high-oxygen conditions; providing anoxic conditions; alternating the step of providing high-oxygen conditions and the step of providing anoxic conditions; and monitoring an outflow from the biofilter chamber for predetermined levels of carbonaceous matter, nitrogenous matter or mixtures thereof.
In one embodiment, the outflow is monitored for one or more of nitrogen content, phosphate content, and organic carbon content. The method of the present invention may further comprise the step of recirculating the contents of the biofilter chamber. In another embodiment, the high-oxygen conditions during the high-oxygen periods are uniform throughout the biofilter chamber. In a further embodiment, the high-oxygen conditions are provided with predetermined periodicity. It is contemplated that high-oxygen and anoxic conditions are provided in alternate periods, wherein, for example, each period lasts between 1 and 12 hours. In a preferred embodiment, each of the periods lasts between 2 and 9 hours, most preferably with each high-oxygen period lasting between 3 and 7 hours, and each anoxic period lasting between 3 and 9 hours.
It is preferred that the biofilter system reduce the amount of carbonaceous matter, nitrogenous matter, and/or mixtures thereof in the outflow to no less than approximately 80% of the original amount of carbonaceous matter, nitrogenous matter, or mixtures thereof in the aqueous source. It is more preferred for the amount to be reduced by no less than approximately 90%.
According to the method of the present invention, the bacteria utilized in the biofilter chamber should be capable of growth in aminobenzene, phenol, monoethylamine, diisopropylamine, or mixtures thereof. In one embodiment, the bacteria may be carried in the biofilter chamber on a solid support, such as, for example, a biotower, a rotating biological contactor, rough stones, slats, plastic media, a microcarrier, and/or media particles. In a preferred embodiment, the bacteria are carried by anionic and hydrophilic media particles having a rough surface, such as ceramic spheres, with a diameter less than 1 mm, or more preferably with a diameter either less than 0.8 mm or less than 0.6 mm. The bacteria may also be present in the biofilter system in suspension, free from a solid support.
It is contemplated that the methods of the present invention are suitable for removal of carbonaceous matter, nitrogenous matter, matter containing phosphate, and/or mixtures thereof from aqueous waste generated by, for example, aquaculture or industrial processes. The aquaculture may be carried out in, for example, a tank, a natural pond or lake, a man-made pond or lake, or cages in open waters. Possible industrial processes include, for example, effluents from the tanning industry, the defense industry (e.g. munitions production), the food industry, the agriculture industry and the chemical industry (e.g. manufacturing of fertilizers).
An aquaculture system of the present invention includes: an aqueous environment; a means for fluidly connecting the aqueous environment with a biofilter system of the present invention; a means for disinfecting an outflow of the biofilter system; and a means for returning the disinfected outflow to the aqueous environment. The biofilter system for aquaculture may further include a pump, and/or means for filtering an outflow from the aqueous environment prior to the outflow entry into the biofilter system. Accordingly, the aqueous environment may be a tank, a man-made pond or lake, a natural pond or lake, or cages in open waters. The present invention is most particularly directed to a method of aquaculture wherein fish are grown in the aqueous environment described herein and the aqueous waste resulting from the aquaculture is treated by the method for removal of carbonaceous matter, nitrogenous matter, matter containing phosphate, and/or mixtures thereof as described above.
The present invention is further directed towards a biofilter system for treating animal waste. A biofilter system for treating animal includes: a first vessel having a first inlet port and a first outlet port, wherein the first vessel contains means for degrading waste solids within the animal waste and means for separating solid and liquid animal wastes; and a second vessel having a biofilter system of the present invention, including a second inlet port fluidly connected to the first outlet port of the first vessel. It is contemplated that the effluent from the first vessel is aqueous.
The present invention is also directed towards a method of removing carbonaceous matter, nitrogenous matter, matter containing phosphate, and/or mixtures thereof from animal waste, by passing the waste through the biofilter system of the present invention. It is preferred that the biofilter system reduce the amounts of carbonaceous matter, nitrogenous matter, matter containing phosphate and/or mixtures thereof in the outflow by no less than approximately 80% of the original amounts in the untreated aqueous waste. Most preferably, the amount is reduced by no less than approximately 90%. It is contemplated that the method of the present invention is useful for treatment of waste of any animal, preferably a farm animal, such as, for example, a pig, a horse, a goat, a sheep, a cow, a chicken, a turkey, an ostrich, an emu, a llama or an alpaca. The biofilter system of the present invention is suitable for treatment of animal waste comprising no more than approximately 10% solid waste. Preferred, is 5% solid waste, and most preferred is less than approximately 1% solid waste.